Production of light-sensitive material for diazotypes



Nov. 18, 1958 i I w. G. HOLLMANN 2,861,008

PRODUCTION OF LIGHT-SENSITIVE MATERIAL FOR DIAZOTYPES F iled Dec. 14, 1953' Fi 6 F5966! Fly '65 m 6c I In ven Z07" Mala er 6.]20'ZZma72 .pound in the design'areas.

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dried to leave the surface layer.

United States Patent M zssino OF'LIGHT-SENSITIVE A ERIAL PRODUCTION FOR-DIAZOTYPES walt rsG- a lmaan lassrfie s rl aas is to de ck Post Qornpany, Chicago, Ill., a corporation of Illinois Application December 14, 1953, Serial No. 398,231

.42 C a m 1- 11 -1-3 The present invention relates to light-sensitive surfaces,

and in particular to those having light-sensitive diazo compounds, for example, diazotype sheets.

Diazotype sheets commonly used are paper coated a layer containing essentially a stable light-sensitive diazo compound with or without related chemical ingredients functioning with respect to stability of the light-sensitive 7 paper, development of the light-sensitive paper, or preserpounds in general are suitably stable over useful periods of time against decomposition in the dark, are resistant to decomposition on moderate exposure to subdued day- Tparency such as a tracing common in the mechanical arts,

which passes ultraviolet light in its clear field portions and which excludes such light at design areas, for example, the lines of a mechanical drawing. The transparency is placed in contact with the light-sensitive surface and subjected to ultraviolet light for a time sufiicient to decompose the diazo compound throughout the layer thereof in the clear field areas, thereby preserving the diazo com- The preserved diazo compound has the ability to couple with certain agents forming dyestufis and such dyestufis are then formed as the permanent record. The dye formation occurs under convation of the developed paper. 7 Light-sensitive diazo comtrolled pH conditions, commonly neutral or alkaline.

The coupling agent employed may be present in the sensitive layer as part of a non-coupling composition, in which case the color development is readily eflected in the presence of moisture and alkali, as for example,'by moist ammonia vapor. In those cases where the coupling agent is not present in the sensitized material, it is applied as a solution, usually alkaline in character. Because alkalinity favors coupling, the diazo compound is commonly stabilized in the light-sensitive material by the presence of acidic material. Such acidic material-is frequently a reducing chemical so that its residue in the final print functions to minimize oxidation in the. clear fields, whereby yellowing is minimized.

The commercial production of light-sensitive diazo surfaces, especially on a paper carrier or base, presents difl'l- H V culties. Among them is the depth of the diazo compound inwardly from the surface exposed to light. The conditions of exposure must be such that the decomposition of the diazo compound is effected throughout that depth in the areas where the field of the transparency calls for decomposition. This difiiculty is met by applying a relatively thinsurface layer containing the diazo compound. To accomplish this, there must be a controlled tion between the means of applying the light-sensitive rnaterial the character of thesheet receiving it. The, .lightsensitive materials are commonly applied as an aquelayer from which the residual water 7 Conventional coating machinery is employed and the character of the paper oiis'liquid to' form a above objectives.

:milSt be predetermined with respect to the'coatinginethod and theeharacter of the coating liquid in order to minimize penetration of the light-sensitive material into the sheet to a depth beyond which it may not be decomposed in .the conventional .or prescribed processing thereof.

"The conventional coating method is to apply an ex ess of the sensitizing liquid, and then to remove" the excess by a suitable doctoring means such as a knife blade or a. knife-like stream of air. Commonly a rotating coating roll is partially immersed in a bath of the liquid and the paper sheet is run over the roll, thereby to acquire adherent film of the solution. The paper is so treated that the liquid only slowly penetrates the sheet. Before penetration has proceeded to an undesired depth, the excess liquid is doctored from the sheet, andithen the sheet is dried. i

Accordingly, in the prior art, both the receiving'paper and the liquid for it must be mutually adapted to each otherfor the objectives above mentioned. *Papers for the purpose are therefore specially prepared'to' 'exa'ct s'pecifica'tionsand as a result they are premium papers relatively expensive on that account.

The present invention aims to dispense with the requirement of predetermined receiving surfaces, such as the special papers mentioned and to provide a new coating -method-which may be used with any material having absorbency for liquid regardless of its absorbent capacity orits rate of absorption, such as wood, newsprint, cotton fabric or even the premium papers alreadymentioned.

It is, therefore, a general object of the present invention to provide a novel method of applying sensitizing solution containing diazo compounds to an absorbent'surface to sensitize such surface to a depth suitableforpenetration by actinic light.

'It is a particular object to form a sensitizedlayeron absorbent material by a transfer method avoiding application and removal of excess.

Various other and ancillary objects and advantages of the present invention will become apparent from the following description and explanation of the invention','as illustrated diagrammatically in the accompanying ing, in Which: v 1 i Fig. 1 represents the processing in general meeting the Fig. illustrates a the coating liquid imposition to be transferred by pressure to an absorbent sheet. i

Fig. 3 represents the absorbent sheet of 2 with the liquid impregnating the entire sheet and in the process of being dried by loss of volatilevehicle.

Fig. 4 represents a tandem processing by coating rolls making two applications to an absorbent sheet.

Fig. 5 represents arubber sheet being brushed withihe liquid to form a film thereon,

Figs. 5a through 5d represent a sequence of stepsin applying said rubber sheet to a wood block,.removing' it, and drying the impregnated surface. i f

Fig. 6 represents abrayer roll being coated by running over blotting paper saturated with the liquid.

Fig. 6a represents the brayer roll having a thin film thereon; Fig. 65 represents the brayer roll being rolled over an absorbent sheet; and Fig. 60 represents the resulting saturated sheet after removal of the brayer roll and ready to be dried.

The present invention provides a new method of applying the light-sensitive material, permits us'eof a wide variety of carriers to he sensitized, and, therefore, provides a new relation between the two. The principal requirements for the present invention are the use of' a transfer surface which is wettable by the sensitizing liquid and which is non-absorbent thereof, and the use of a Patented Nov. 18, 1958 drawfiat platen bearing a thin layerof receiving carrier which has a surface absorbent of the sensitizing liquid. It is not even essential that the absorbent character of the receiving carrier be uniform over the area employed. Wood is an example of absorbent material having a surface of nonuniform absorbency,-resulting from'the grain of the wood presenting relatively harder and softer regions. V 7 surfaces, and the like are substantially uniform in character, inherently resulting from the processing in manufacture. A

The present invention contemplates the application of a thin film of sensitizing liquid to a non-absorbent transfer surface wetted thereby, such surface being relatively smooth and free from minute hills and valleys in order that the film normally adhering to it is substantially uniform in its thickness. The transfersurface wet with such film is then brought into pressure contact with the surface of the carrier to be sensitized. The absorbencyof the carrier takes up the contents of the film during contact, the time of which is of necessity controlled so that v the surfaces are not separated until'the absorption is complete. During contact the surfaces are relatively stationary to each other. On separation, the transfer surface is relatively dry and the carrier is moist. Then the sensitized carrier is dried.

, In the case of very thin absorptive sheets, as of paper,

dried from both faces. The thickness of the sheet being sensitized need not be limited, but whether or not it is Paper, cotton fabric, gelatin sensitized from face to face de ends u on the thickness p p .as indicated by the stippling 24 in Fig. 3. The arrows 25 of the layer thereof which contains the diazo compound, and that depends upon the thickness of the film on the transfer surface as well as upon the thickness of the sheet having the absorbing surface. The said layer is purposely limited in thickness so that its diazo content may.

be wholly decomposed throughout the thickness under -the conditions of exposure to be used thereon. The conditions of exposure, of course, may vary over a wide range, but in commercial practice they are specified.

Even the thickness of the tracing sheet is a factor in- .volved in the conditions of exposure. The thickness of the liquid film originally placed on the transfer surface is the means for controlling the thickness of the sensitive 'layer with respect to any particular carrier.

The transfer step may be effected by bringing together I like areas of the two surfaces, the transfer surface already bearing a liquid film of predetermined thickness. This method corresponds to printing with a platen press. Preferably, however, for commercial production, the transfer step is applied in the manner of printing with rotary presses. The transfer surface in such method is in the form of a cylinder on the surface of which the liquid film is continually applied at one region and removed in another. The receiving carrier moves at the same speed as the periphery of the cylinder, and the time of contact for transfer is readily adjusted by regulating the arcover which the carrier and the cylinder remain in contact. This is readily accomplished when the carrier is sufficiently flexible to follow the curvature of the transfer cylinder. The greater the rate of absorption of the carrier surface for the liquid, the smaller may be the arc of contact, for any fixed speed of the rotating cylinder. Thus, the papers commonly used for receiving excess of the liquid followed by doctoring, may be used in the present invention as well as papers which are not at finish, being freer from such minute hills and valleys.

.Low-finish papers may not be adequately sensitized by one impression thereon of the film-carrying transfer sut- Others have a fine or high increased by a second transfer.

operation are 7 identical with 'ing moved away. Then the block face. In such a case. more than one such impression may be made, one after the other, before drying.

The sensitizing solution may vary widely in viscosity, and also in its wetting power. Wetting agents may be added to facilitate wetting the transfer surface and also penetration of the absorbent surface. Thickening agents such as starch and certain water dispersible cellulose derivatives may be present to increase the viscosity of the solution as a means for minimizing penetration of the sensitizing liquid into the carrier surface. The sensitizing liquids maty be otherwise formulated as in the prior art to contain acidic material, reducing material and coupling agents, as is well known.

Mechanically, the invention may be carried out in many ways. In Fig. 1 the numeral 10 represents a base with an absorbent face to be sensitized. The numeral 11 represents a body having a non-absorbent transfer surface 12 with a thin liquid film 13 thereon for application to the base 10. As positioned the transfer body 11 is shown as having already transferred a portion of its film to the absorbent base, as the body 10 rolls in the direction of arrow 14. The transferred portion is represented by the dotted region 15. The block 16 represents the subsequent step of drying the applied liquid 13.

. Fig. 2 represents a platen 20, part of which has been liquid of film 21 is transferred by contact, indicated by arrow 23. The sheet 22 is sufficiently thin so that the liquid 21 thoroughly impregnates the sheet throughout represent subsequent processing to dry the impregnated sheet 22.

, Fig. 4 shows a tank 30 having the sensitizing liquid therein into which dips a rotating roll 32. The roll 32 picks up a supply of liquid 31 an excess 33 of which .is doctored away by the doctor blade 34 to leave a thin film 35 on the roll. In contact with and into .the path of the thin film there is a metal transfer roll 36 rotating oppositely which picks off a thin film 37 of the liquid to be applied to a web of. paper 38. The paper web approaches the roll at any suitable place and moves with it over an arc to an idler roll 39, which .is circumferentially adjustable about the axis of roll 36 in order to vary the arc of contact.

. When the treated web indicated by the numeral 40 is insufficiently supplied with sensitive material fora particular purpose, the content of sensitive material may be Preferably, the process which the parts and the that already described. The twice-treated web 42 leaves the second unit 41 andis moved through a suitable drier indicated by the is repeated by a like unit 41 of numeral 43.

Another method is illustrated in Fig. 5 wherein a rubber sheet 50 is supplied with a thin film of liquid 51 by applying the same by a brush 52. Fig. 5a represents a block of wood 53 to be sensitized and shows the film-carrying transfer sheet 50 about to be applied to the wood. Fig. 5b shows the wood and rubber in contact so that the liquid of film 51 is transferred to and absorbed by the wood block as indicated by the stippling 55 in Fig. 50, which shows the depleted rubber sheet 50 be- 53 is dried, as by an infra-red lamp 56 shown in Fig. 5d.

Fig. 6 represents another modification in which a sheet a piece of blotting paper 61 62. Over this a brayer roll 63 is moved with with a portion of liquid already transferred to the sheet as indicated by the stippling 66. Fig. 6c shows the resulting impregnated sheet 65 ready for a dryer and the brayer roll 63 being moved away. I

The following examples illustrate the inventioni Example 1 A light-sensitive fluid is prepared containing the following:

100 ml. water 2 gm. p-diazo-dimethyl-aniline zinc chloride double salt 2 gm. 2,3-dihydroxynaphthalene-G-sulfonic acid 2 gm. tartaric acid 0.2 gm. saponin A thin coating of the above solution is brushed onto a sheet of gum rubber, as illustrated in Fig. 5. The wetted rubber is then pressed onto a smooth face of wood. Because of the absorbency of the wood, momentary contact is suflicient to transfer all liquid to the wood. On separation of the rubber and the wood, the rubber transfer surface is substantially dry. The moistened surface of the Wood is then dried as by exposure of infra-red radiation, as shown in Fig. 5d, or by placing it in a darkened oven or atmosphere.

Any absorptive cloth or paper sheet may be used in the same manner as the wood.

The product of the foregoing sensitization, whether on wood, paper or cloth may be placed under artransparency carrying a design and exposed to strong actinic light until the yellow diazo compound in the sensitized layer has been bleached out in the field areas of.the transparency. The above formulation includes the coupling agent so that after exposure the undeveloped light-printed surface is developed in an atmosphere of moisture and ammonia. The ammonia neutralizes the tartaric acid and provides alkalinity favoring the coupling of the diazo compound 7 atthe design areas and the coupling agent forming at dyestuif' in areas conforming exactly to the design on the transparency.

Example 2 A light-sensitive fluid having induced viscosity is formed as follows:

5 gm. starch 1 gm. p-diazo-diethyl-aniline zinc chloride double salt 1 gm. 2,3-dihydroxynaphthalene-6-sulfonic acid 1 gm. citric acid 110 ml. water The starch is first dispersed in 100 ml. of cold water, heated to 180 F. for 5 minutes, and then cooled. The remaining ingredients are dissolved in 10 ml. of water and stirred into the starch paste, forming a viscous fluid. As an example of one of numerous methods of applying the above liquid to a transfer surface, there is used a piece of blotting paper saturated with the fluid and placed on a hard flat surface such as glass as illustrated in Fig. 6. A soft rubber brayer roll isrun over the saturated blotter, thereby acquiring a thin film of thefluid. The brayer having the said film is then run over an absorbent paper such as newsprint in a simple rolling operation, the newsprint being sufiiciently absorptive to effect transfer substantially momentarily. The moist sensitized sheet is then dried in any suitable manner, preferably quickly by subjecting it to infra-red rays.

In the foregoing example, the quantity of sensitizing fluid available for the highly absorptive carrier is insufficient to permit other than a very thin layer of the liquid at the surface of the sheet. The composition employed contains the coupling agent so that the, print may be developed by ammonia fumes, or by the application of any alkaline solution. A deep blue image results.

6 Example 3 A'thickened sensitizing solution is formed as follows? 5 gm. low' viscosity chlorinated starch 1 gm. p-diazo-ethyl-benzyl-aniline zinc chloride double salt l gm. citric acid 1.25 gm. methyl cellulose (4000 cps.) ml. water The'starch is stirred into 100 ml. of water, heated to 200 F. for 30 minutes and then cooled. The diazo compound and citric acid are then added and the mixture stirred until solution is complete. The methyl cellulose is added to 25 ml. of water at 180 F. and allowed to soak at that temperature for 20 minutes. Then the mixture is cooled to 50 F. and stirred until smooth. The two fluids are then mixed. 7

The above solution may be applied in any manner to a transfer roll non-absorbent thereof, either of rubber, or of metal, or of numerous synthetic compositions having hydrophilic surfaces whereby a smooth thin film is readily formed thereon. Then the film is merely transferred by contact to an absorbent surface in the suitable manner while the two surfaces are in stationary relation toeach other during contact.

"Since the foregoing composition does not contain a coupling agent, the dry sensitized material, after being light-printed is developed by application of a developing solution in a well-known manner. A suitable developing solution is as follows:

0.5 gm. phloroglucinol 5 gm; borax v 100 ml. water From the foregoing it will be appreciated that the invention is not limited to use of the materials or com-' positions specifically mentioned, nor to any precise method of carrying it out. Numerous changes and modifications are contemplated as falling within the scope of the appended claims.

I claim:

1. The method which comprises forming on a transfer surface a penetrating fluid film containing essentially a fluid vehicle and normally solid content dispersed in said vehicle including essentially light-sensitive diazo compound capable of decomposition by actinic light and capable of union with a coupling agent to form a dye, the transfer surface being wettable by and nonabsorptive of said fluid, transferring the contents of said film to a body having a receiving surface by bringing the film on the transfer surface into contact with the receiving surface and then separating the said two surfaces while maintaining the contacting portions of said two surfaces stationary relative to each other during said contact, the material of the body providing said receiving surface being absorptive of said fluid whereby to remove the film from said transfer surface and to deposit said lightsensitive compound within the body and in the vicinity of the receiving surface. 2. Thefmethod which comprises forming on a transfer surface a penetrating fluid film containing essentially a fluid vehicle and normallysolid content dispersed in said vehicle including essentially light-sensitive diazo compound capable of decomposition by actinic light and capable of union with a coupling agent to form a dye, and also containing at least one coupling agent therefor, the transfer surface being wettable by and non-absorptive of said fluid, transferring the contents of said film to a body having a receiving surface by bringing the film on the transfer surface into contact with the receiving surface and then separating the said two surfaces while maintaining the contacting portions of said two surfaces stationary relative to each other during said contact, the material of the body providing said receiving surface being absorptive of said fluid whereby to remove the film from said transfer surface, and to deposit said light- .7 sensitive compound andsaid coupling agent within the body and in the vicinity of the receiving surface.

3. The method which comprises forming on a transfer surface a penetrating fluid film containing essentially volatile vehicle and normally solid content dispersed in said vehicle including essentially light-sensitive diazo compound capable of decomposition by actinic light and capable of" union with a'coupling agent to 'form a dye, the transfer surface being-wettable by and non-absorptive of said fluid, transferring the contents .of said film to a body having a receiving'surface by bringing the film on the transfer surface into contact with the receiving 'surface and then separating the said two surfaces while maintaining the contacting portions of said two surfaces stationary relative to each other during said contact, the material of said body providing said receiving surface being absorptive of said fluid whereby to remove the film from said transfer surface and locate all the fluid within said body and in the vicinity of the receiving surface, and evaporating volatile vehicle from the receiving surface.

4. The method which comprises forming on a 'transfer surface a penetrating fluid film containing essentially aqueous vehicle and normally solid content dispersed in said vehicle including essentially light-sensitivediazo compound capable of decomposition by actinic light and capable of union with a coupling agent to form a dye, the transfer surface beingwettable by and non-absorptive of said fluid, transferring the contents of said film to a body having a receiving surface by bringing the film on the transfer surface into contact with the receiving surface and then separating the said two surfaces while maintaining the contacting portions of said two surfaces stationary relative to each other during said contact, the material of said bodyproviding said receiving surface being absorptive of said fluid whereby to remove the 'film from said transfer surface and locate all the fluid within said body and in the vicinity of the receiving surface, and evaporating the aqueous vehicle from the receiving surface. 7

5. The method which comprises forming on a transfer surface a penetrating fluid film containing essentially aqueous vehicle and normally solid content dispersed in said vehicle including essentially light-sensitive diazo compound capable of decomposition by actinic light and capable of union with a coupling agent to form a dye, and also containing at least one coupling-agent, the transfer surface being wettable by and non-absorptive of said fluid, transferring the contents of said film to a body having a receiving surface by bringing the film on the transfer surface into contact with the receiving surface and then separating the said two surfaces while maintaining the contacting portions of said two surfacesstationary relative to each other during said contact, the material of said body providing said receiving surface being absorptive of said fluid whereby to remove the film from said transfer surface and locate all the fluid within said body and in the vicinity of the receiving surface, and evaporating the aqueous vehicle from the re, ceiving surface.

6. In the manufacture of dry light-sensitive sheet material containing a light-sensitive diazo compound decomposable by actinic light for light-printing exposure and development to produce diazo-types, the steps of an adherent film of an aqueous liquid containing essentially the light-sensitive diazo compound, which liquid is penetrating with respect to the hereinafter-mentioned sheet material, transferring the contents of said film to an absorptive face of sheet material by placing the film in contact with said sheet, and drying the resulting sheet, whereby the fluid -is absorbed by said face, and after said absorption removing thetransferbody.

7 The process of claim 6 wherein the sheet is thicker than the said dried layer containing the light-sensitive compound.

8. The process of claim 6 wherein the sheet is so thin that the said dried layer containing the light-sensitive compound'extends from face to face.

9. In the manufacture of dry light-sensitive sheet material containing a light-sensitive diazo compound decomposable by actinic light for light-printing exposure and development to produce diazo-types, the steps of forming on a non-absorptive surface of a transfer body an adherent film of an aqueous liquid containing a noncoupling composition of the light-sensitive diazo compound and a dye-forming coupling agent therefor, which liquid is penetrating with respect to the hereinaftermentioned sheet material, transferring the contents of said film to an absorptive face of sheet material by placing the film in contact with said sheet, and drying the resulting sheet.

10.. The process of claim 9 wherein the sheet is thicker than the said dried layer containing the light-sensitive compound.

'11. The process of claim 9 wherein the sheet is so thin that the said dried layer containing the light-sensitive compound extends from face to face.

12. In the manufacture of dry light-sensitive sheet material containing a light-sensitive diazo compound decomposable by actinic light for light-printing exposure and development to produce diazo-types, the method of applying light-sensitive material which comprises forming on a non-absorptive surface of a transfer body an adherent film of an aqueous liquid containing the lightsensitive diazo compound, which liquid is penetrating with respect to the hereinafter-mentioned sheet material, transferring the contents of said film to an absorptive faceof sheet material by placing the film in contact with said sheet, repeating the said steps a suflicient number of times so that the thickness of the hereinafter-mentioned dried layer containing the light-sensitive compound is readily penetrated by actinic light to a sufficient extent to decompose all the light-sensitive diazo compound in the path of the light, and drying the resulting sheet to provide therein a dried layer containing the non-volatile contents of the liquid.

References Cited in the file of this patent UNITED STATES PATENTS 890,309 Smith June 9, 1908 1,756,400 Schmidt et al. Apr. 29, 1930 2,243,486 Ormond May 27, 1941 2,293,690 Harrigan Aug. 18, 1942 2,634,677 Klimkowski Apr. 14, 1953 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,861,008 November 18, 1958 Walter G. Hollmann It is herebfi certified that error appears in the -printed specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 5, line 38, for "forming at" read forming a column 8, line 8, after "sheet", second occurrence, strike out the comma; same line, strike out ''and drying the resulting sheet" and insert the same after "body" and before the period in line 10, same column; line 28, claim 9, after "sheet," insert whereby the fluid is absorbed by said face, and after said absorption removing the transfer body Signed and sealed this 3rd day of March 1959.

(SEAL) Attest:

KARL H. AXLINE ROBERT C. WATSON Attesting Officer Commissioner of Patents 

1. THE METHOD WHICH COMPRISES FORMING ON A TRANSFER SURFACE A PENETRATING FLUID FILM CONTAINING ESSENTIALLY A FLUID VEHICLE AND NORMALLY SOLID CONTENT DISPERSED IN SAID VEHICLE INCLUDING ESSENTIALLY LIGHT-SENSITIVE DIAZO COMPOUND CAPABLE OF DECOMPOSITION BY ACTINIC LIGHT AND CAPABLE OF UNION WITH A COUPLING AGENT TO FORM A DYE, THE TRANSFER SURFACE BEING WETTABLE BY AND NONABSORPTIVE OF SAID FLUID, TRANSFERRING THE CONTENTS OF SAID FILM TO A BODY HAVING A RECEIVING SURFACE BY BRINGING THE FILM ON THE TRANSFER SURFACE INTO CONTACT WITH THE RECEIVING SURFACE AND THEN SEPARATING THE SAID TWO SURFACES WHILE MAINTAINING THE CONTACTING PORTIONS OF SAID TWO SURFACES STATIONARY RELATIVE TO EACH OTHER DURING SAID CONTACT, THE MATERIAL OF THE BODY PROVIDING SAID RECEIVING SURFACE BEING ABSORPTIVE OF SAID FLUID WHEREBY TO REMOVE THE FILM FROM SAID TRANSFER SURFACE AND TO DEPOSIT SAID LIGHT-SENSITIVE COMPOUND WITHIN THE BODY AND IN THE VICINITY OF THE RECEIVING SURFACE. 